Well I can show you pictures of mine that are a year old, never turned, never moved, and completly round. They do grow naturally into a ball or oval, without rolling across the substrate. If you ever have any spores grow in your gravel, you will see they start as green little tufts and then form into a ball, or perhaps it is more of a blob that I presumed would form a ball!
They are however under a current, so I guess that may be why mine remain round or oval. I have occasionaly had one split. I have also had two fuse together, and I have some piled on top of each other, and they have still stayed round.
I grow mine in unheated, room temp water, which in the winter time is around 65F. They come from cold water in Japan, northern Europe, and Iceland. My lighting is about 2 watts per gallon with no C02 injected into the water. I doubt most people I sell them to keep them in as cool a water as I do. I have sold somewhere around 300 of them and nobody has reported any problem growing this plant, temp, lighting, or any other factor. Florida Aquatic sells them to stores thru their distributors as "Moss Ball" and tells the stores they remove phosphate and nitrogen from the water, which is very unlikely considering how slow a grower they are. Florida Aquatic imports them from Oriental Aquarium in Singapore.